Cameras that take moving pictures and still pictures have an ADC that converts the image data detected with an image sensor to digital data. This digital data is then processed by an image processor or stored in a nonvolatile storage medium.
Because the analog signal output from the image sensor is a typically weak signal, the held sample is first amplified by an amplifier and then output to a converter in a latter stage for conversion to a digital signal. The amplifier is usually set for operation with a high operating current so that even when an analog signal of maximum amplitude is input, it is still possible to output a distortion-free waveform. However, when a small amplitude analog signal is input continuously, although a low operating current is enough for the small amplitude analog signal, a large operating current is employed. The use of these large operating currents can reduce battery life and cause other deleterious problems.
Some examples of prior art camera systems are PCT Publication No. WO2008052569, and U.S. Patent Pre-Grant Pub. Nos. 2001/008268; 2003/011698; 2006/109360; and 2006/237629.